Car charging: Charging (AC) vs (USB)

[rockdawg]

I am trying get a car charger that will charge my EVO in fast charge mode (charging (AC)) or whatever t's called. I bought a a griffin 2-port usb car charger. It says it's 1 amp, but I was afraid it would only be 500mA per port. Stupidly, I forgot to bring along my USB cable so I bought one there to make sure the charger would make my phone show as charging in AC mode. The only cable they had was a Rocketfish mini USB that included an adapter to make it micro USB. I took this out to my car and tried ti and to my suprise, my phone read charging (AC). I re-inserted botht the cable and the charger several times to make sure and it always showed AC mode.

When I got home and tried any of my regular cables, it always shows as charging (USB). Why is that? Could the cable really make a difference?

 

[kennycrudup]

That happened 'cause the mini-to-micro adapter tied the data lines together, which is the standard for indicating high-current ("AC") charging.

I was looking for a high-power-charge car adapter too- so if you're within your return period go back to Best Buy and get the generic RocketFish micro-USB car charger; it ties the data lines together and will rapid charge. Took me 3 tries to find a brand that did it right.

Turns out you need rapid charging if you're in a 4G area and using Navigation; the combination of those three heavy power sinks will drain your battery faster than a USB-signaling charger (which some car chargers will report for compatibility with older devices) can supply.

 

[deparson]

The solution to make your charger work with all cables is to short the two middle pins of the USB port ( called D+ and D-).

This will tell your phone it can ask for more than .5A of power and put it into fast charge mode aka AC charging.

If you get the charger apart it is an easy solder job for most devices.

 

[Caitlyn McKenzie]

More detailed explanation:

The phone can ALWAYS ask for more than .5A of power. Your PC can, in theory, give the phone 1A of power if it wants to. However, by spec, they're only required to provide .5A, so anything above that is up to each computer manufacturer (specifically, the manufacturer of the USB chips in your PC).

Shorting the data pins tells the phone to ASSUME that there is more power available, instead of USB spec of reverting to .1A USB power (which is the maximum a device can use without asking for additional power).

 

[forceOnature]

If you don't have the means of modifying the USB cable yourself, take a look at this cable at the XDA forums:

xda-developers

 

[rockdawg]

Thanks for all the input guys. I'll look into altering my charger.

 

[mgwerks]

Good tips!